Quantification of Left Ventricular Interstitial Fibrosis in Asymptomatic Chronic Primary Degenerative Mitral Regurgitation

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Abstract
Background—: The optimum timing of surgery in asymptomatic patients with chronic severe primary degenerative mitral regurgitation (MR) remains controversial, and further markers are needed to improve decision-making. There are limited data that wall stress is increased in MR and may result in ventricular fibrosis. We investigated the hypothesis that chronic volume overload in MR is a stimulus for myocardial fibrosis using T1-mapping cardiac MRI. Methods and Results—: A cross-sectional study of 35 patients (age 60±14 years) with asymptomatic moderate and severe primary degenerative MR (mean effective regurgitant orifice area, 0.45±0.25 cm) 2 with no class I indication for surgery were compared with age and sex controls. Subjects were studied with cardiopulmonary exercise testing, echocardiography, and cardiac MRI. Longitudinal and circumferential myocardial deformation was reduced with MR when left ventricular ejection fraction (67%±10%) and N-terminal pro B Natriuretic peptide (126 [76–428] ng/L) were within the normal range. Myocardial extracellular volume was increased (0.32±0.07 versus 0.25±0.02, P r =0.62, P r =0.41, P r =−0.60, P r =−0.46, P 2 max ( r =−0.51, P r 2 =0.42, P <0.01). Conclusions—: Patients with asymptomatic MR demonstrate a spectrum of myocardial fibrosis associated with reduced myocardial deformation and reduced exercise capacity. Future work is warranted to investigate whether left ventricle fibrosis affects clinical outcomes.

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